Study of the high-temperature pyrolysis of propene by determination of H and D atoms formed from partially deuterated propenes heated behind shock waves

Abstract

Very dilute mixtures of CD{sub 2}CHCH{sub 3}, CH{sub 2}CDCH{sub 3}, and CH{sub 2}CHCD{sub 3} were pyrolyzed at 1500-1800 K behind incident shock waves at an average pressure of 0.42 atm and behind reflected waves at 2.8 atm. Analysis for H and D using resonance absorption spectroscopy showed that propene dissociates partly by formation of hydrogen atoms and allyl radicals, (1), and partly by formation of vinyl and methyl radicals, (2). Both of these unimolecular dissociation reactions of propene are in the intermediate falloff region at our pressures and temperatures. For (1) we find k{sub 1} = 3.5 {times} 10{sup 12} exp(-75 kcal/RT) s{sup {minus}1} at 0.42 atm and k{sub 1} = 3.6 {times} 10{sup 13} exp(-80 kcal/RT) s{sup {minus}1} at 2.8 atm. For (2) we find k{sub 2} = 8.2 {times} 10{sup 12} exp(-80 kcal/RT) s{sup {minus}1} at 0.42 atm and k{sub 2} = 2.3 {times} 10{sup 13} exp(-80 kcal/RT) s{sup {minus}1} at 2.8 atm. Estimated uncertainties are factors of 1.5 in (1) and 2 in (2).